Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming, and ultimately expensive endeavors. As a result, over the years, a significant amount of added emphasis has been placed on well monitoring and maintenance.
In terms of interventional monitoring and maintenance in subsea hydrocarbon operations, various tools and testing devices may be provided by way of a subsea landing string system. Such a system may enable completion, flow testing, intervention, and other subsea well operations to be performed from a floating vessel. Generally, the landing string is run down through a marine riser and access to the well is achieved through a BOP (blowout preventer). The BOP contains a number of features used to ensure well integrity, including any of several shearing and sealing rams, as well as some operation-specific features, such as orientation pins used to define the orientation of the landing string.
One of the more significant considerations in designing a subsea landing string is the space-out of the landing string within the BOP. The “space-out” refers to the location of various features of the landing string relative to the relevant features of the BOP, in particular shearing and sealing rams, as well as orientation pins and other features. It is important that the landing string be configured in such a way that the necessary BOP functionality (e.g., sealing) can be maintained.
With such landing string challenges as noted above, one feature that may be included, particularly when running well completions, is a Tubing Hanger Orientation Joint (THOJ). This is a section of the landing string that defines the rotational orientation of the landing string relative to the BOP in order to properly install or interface with the tubing hanger for vertical production trees. In many cases the THOJ achieves this orientation through the use of an orientation helix and a slot (keyway) or the like, which interact with a pin or key projecting into the BOP interior. Typically these orientation features gradually impose the correct orientation over some distance of vertical travel as the landing string is lowered into the BOP.
Unfortunately, the required distance of vertical travel to achieve proper orientation contributes to a minimum height requirement for the orientation joint. This in turn, may conflict with the desired BOP space-out for performing certain well operations. Addressing this conflict may potentially be achieved by performing the necessary operations in multiple runs, each with a different landing string configuration. However, the requirement of multiple runs and landing string change outs would be quite time-consuming, dramatically increasing the cost of operations.